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  Automotive tandem alternator having reduced axial length and improved structure for effectively dissipating heat generated by rectifiersUSPTO Application #: 20070247011Title: Automotive tandem alternator having reduced axial length and improved structure for effectively dissipating heat generated by rectifiers Abstract: According to the invention, a tandem alternator includes a rotary shaft, a first and a second power generation unit arranged in tandem in the axial direction of the rotary shaft, a housing accommodating the power generation units and having a plurality of air holes formed through a front end wall thereof, a pulley provided on a front end portion of the rotary shaft which protrudes outside from the first end wall of the housing, and a first and a second rectifier working to respectively rectify AC powers output from the first and second power generation units. The first rectifier is so fixed to the outer surface of the front end wall of the housing as to be located on the radially outside of the pulley and cover only part of the air holes. The second rectifier is fixed to the outer surface of a rear end wall of the housing. (end of abstract) Agent: Oliff & Berridge, PLC - Alexandria, VA, US Inventors: Akiya Shichijoh, Shin Kusase, Takeo Maekawa USPTO Applicaton #: 20070247011 - Class: 310112 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20070247011. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATION [0001]This application is based on and claims priority from Japanese Patent Application No. 2006-118104, filed on Apr. 21, 2006, the content of which is hereby incorporated by reference into this application. BACKGROUND OF THE INVENTION [0002]1. Technical Field of the Invention [0003]The present invention relates generally to electric generators. More particularly, the invention relates to a tandem alternator for a vehicle, which has a reduced axial length and an improved structure for effectively dissipating heat generated by rectifiers included therein. [0004]2. Description of the Related Art [0005]Japanese Patent First Publication No. H11-98789 discloses a tandem alternator for a vehicle, which includes a single rotary shaft and a front-side and a rear-side power generation unit that are arranged in tandem in the axial direction of the rotary shaft. [0006]The tandem alternator further includes a pulley mounted on a front end portion of the rotary shaft and a first and a second rectifier that work to respectively rectify AC powers output from the front-side and rear-side power generation units into DC powers. The first and second rectifiers each generate a large amount of heat during operation of the alternator. To effectively dissipate the heat and minimize the distances from the rectifiers to the corresponding power generation units, the first and second rectifiers are respectively arranged at a front and a rear portion of the alternator. [0007]More specifically, the tandem alternator includes a front end frame, a center frame, a housing, and a rear end frame, all of which together enclose both the front-side and rear-side power generation units. The first rectifier is fixed to an outer surface of the center frame, and is thus located inside the front frame. On the other hand, the second rectifier is fixed to an outer surface of the rear frame. [0008]With the above arrangement, however, the total axial length of the tandem alternator is increased. This is because the first rectifier, which is interposed between the front and center frames, occupies a dedicated length in the axial direction of the rotary shaft. [0009]Consequently, in installation of the tandem alternator to an engine of the vehicle, it may be difficult to suitably arrange the alternator without causing interference between the alternator and an inlet or exhaust pipe of the engine. [0010]Accordingly, it is desired to reduce the axial length of the tandem alternator while securing effective dissipation of the heat generated by the first and second rectifiers. SUMMARY OF THE INVENTION [0011]The present invention has been made in view of the above-mentioned problems. [0012]It is, therefore, a primary object of the present invention to provide a tandem alternator which has a reduced axial length and an improved structure for effectively dissipating heat generated by rectifiers included therein. [0013]According to a first embodiment of the invention, there is provided a tandem alternator which includes a rotary shaft, a pulley provided on an end portion of the rotary shaft, a first and a second electric power generation unit, a housing, and a first and a second rectifier. [0014]The first and second electric power generation units are arranged in tandem in an axial direction of the rotary shaft. [0015]The housing rotatably supports the rotary shaft and accommodates therein both the first and second electric power generation units. The housing has a first and a second end wall that are apart from each other in the axial direction of the rotary shaft with the first and second electric power generation units intervening therebetween. The first end wall is closer to the first electric power generation unit than the second electric power generation unit. The second end wall is closer to the second electric power generation unit than the first electric power generation unit. The housing also accommodates therein the rotary shaft with the end portion of the rotary shaft protruding outside from the first end wall of the housing. The housing has a plurality of air holes that are formed through the first end wall of the housing and located outside the pulley in a radial direction of the rotary shaft. [0016]The first and second rectifiers work to respectively rectify AC powers output from the first and second electric power generation units into DC powers. The first rectifier is so fixed to an outer surface of the first end wall of the housing as to be located outside the pulley in the radial direction of the rotary shaft and cover only part of the air holes. The second rectifier is fixed to an outer surface of the second end wall of the housing. [0017]With the above arrangement, the first and second rectifiers are sufficiently apart from each other in the tandem alternator. Consequently, during operation of the tandem alternator, heat generated by the first and second rectifiers can be effectively dissipated, and electrical interference between the first and second rectifiers can be reliably prevented. [0018]Further, with the above arrangement, both the distances between the first rectifier and the first power generation unit and between the second rectifier and the second power generation unit are made sufficiently short, thus effectively suppressing resistance losses occurring therebetween. [0019]Moreover, since the first rectifier is arranged on the radially outside of the pulley, they share a common length in the axial direction of the rotary shaft. In other words, the first rectifier does not occupy a dedicated length in the axial direction. Consequently, with the above arrangement, it is possible to minimize the length of the tandem alternator in the axial direction of the rotary shaft. [0020]Furthermore, since the first rectifier covers only part of the air holes formed through the first end wall of the housing, it is possible for a sufficient amount of cooling air to flow through the other uncovered air holes. In addition, since the first rectifier is exposed to the cooling air through the air holes covered thereby, the heat generated by the first rectifier can be further effectively dissipated. [0021]Accordingly, compared to the above-described conventional tandem alternator, the tandem alternator according to the first embodiment of the invention has a reduced axial length and an improved structure for effectively dissipating heat generated by the first and second rectifiers. Continue reading... Full patent description for Automotive tandem alternator having reduced axial length and improved structure for effectively dissipating heat generated by rectifiers Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Automotive tandem alternator having reduced axial length and improved structure for effectively dissipating heat generated by rectifiers patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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